Inserts with Swellable Elastomer Seals for Side Pocket Mandrels

ABSTRACT

Improved inserts for use in side pocket mandrels which include one or more annular sealing elements that are formed of an elastomeric material that swell in response to heat or fluid saturation. When the insert is emplaced within a side pocket mandrel, the swellable elastomer can then be swelled, using either heat or fluid saturation, to cause the sealing element(s) to expand and seal against the seal bore of the side pocket mandrel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to devices and methods for forming seals within tubular members. In particular aspects, the invention relates to devices and methods for sealing inserts within a side pocket mandrel.

2. Description of the Related Art

Gas lift arrangements are used to improve the rate of production of hydrocarbons from a well by enhancing flow through a production tubing string. Gas lift valves are inserts that are typically removably emplaced in side pocket mandrels in a production string. Gas is then injected into the annulus surrounding the production string. The gas is then transmitted by the gas lift valves from the annulus to the flowbore of the production tubing string. Gas lift arrangements are described in U.S. Pat. No. 7,360,602 entitled “Barrier Orifice Valve for Gas Lift” issued to Kritzler et al. and U.S. Pat. No. 6,810,955 entitled Is “Gas Lift Mandrel” issued to Roth et al. These patents are owned by the assignee of the present application and are hereby incorporated by reference.

Dummy gas lift valves are inserts that are placed into a gas lift side pocket mandrel to entirely close off flow through the side pocket mandrel. Typically, dummy gas lift valves employ stacks of generally v-shaped elastomeric seals (i.e., v-rings) to form a fluid seal against a surrounding seal bore of the side pocket mandrel. The v-ring seals are energized to seal by differential pressure, which isolates fluid communication through the side pocket mandrel. When the seal bores of the side pocket mandrel get eroded or otherwise damaged, the v-rings are no longer able to fully seal and prevent pressure integrity loss.

Other flow control devices are often used within side pocket mandrels, including water flood valves and chemical injection valves.

SUMMARY OF THE INVENTION

In preferred embodiments, the invention provides improved inserts for use in side pocket mandrels and methods of sealing such inserts within side pocket mandrels. In preferred embodiments, the insert includes an insert body that carries one or more annular sealing elements that are formed of an elastomeric material that swells in response to heat or fluid saturation. When the insert is emplaced within a side pocket mandrel, the swellable elastomer can then be swelled, using either heat or fluid saturation, to cause the sealing element(s) to expand and seal against the seal bore of the side pocket mandrel. In one preferred embodiment, the insert is a dummy gas lift valve which will block fluid flow through the side pocket. In an alternative embodiment, the insert is a gas lift valve which selectively transmits gas from the surrounding annulus into the primary flowbore of the gas lift mandrel. In still other embodiments, the insert is another flow control device, such as a chemical injection valve or a water flood valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein:

FIG. 1 is a side, one-quarter cross-sectional view of an exemplary dummy gas lift valve constructed in accordance with the present invention.

FIG. 2 is a side, cross-sectional view of an exemplary side pocket mandrel containing a dummy valve constructed in accordance with the present invention.

FIG. 3 is a side, cross-sectional view of the side packet mandrel and dummy valve shown in FIG. 2, now with the dummy valve having been sealed within.

FIG. 4 is a detail cross-sectional view depicting a sealing element in its unexpanded state.

FIG. 5 is a detail cross-sectional view depicting the sealing element of FIG. 4, now in an expanded state.

FIG. 6 is a side, cross-sectional view of an alternative embodiment of the invention incorporating a gas lift valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an exemplary dummy gas lift valve 10 that has been constructed in accordance with the present invention. The dummy valve 10 includes a generally cylindrical valve body 12 which is preferably made up of an upper body portion 14 and a lower body portion 16 affixed to one another via a threaded connection 18. The upper axial end of the valve body 12 presents a threaded portion 20 which permits the dummy valve 10 to be affixed to a running tool. The valve body 12 preferably carries a pair of annular sealing members 22, 24 which are fashioned from an elastomeric material. The sealing members 22, 24 are preferably formed from an elastomeric material that is physically swellable in response to a particular stimulus. In a currently preferred embodiment, the elastomeric material will swell or expand in response to contact with wellbore fluids, including water and/or hydrocarbon fluids. Elastomeric materials of this type are described in, for example, U.S. Pat. No. 5,384,370 issued to Vondracek et al., entitled “Rubbers Swellable with Water and Aqueous Solutions and the Method for Producing the Same” and U.S. Pat. No. 4,590,227 issued to Nakamura et al., entitled “Water-Swellable Elastomer Composition.” Preferably, the sealing members 22, 24 are solid annular rings. In preferred embodiments, the energizing fluid may be a hydrocarbon fluid or water, or a mixture of both, depending upon the particular composition of the sealing element 22, 24. Thus, the sealing members 22, 24 can be selectively changed from a first, reduced-size, condition to a second, enlarged size condition.

FIGS. 2 and 3 depict a section of an exemplary side pocket mandrel 26 of a type which is well-known in the art. The side pocket mandrel 26 is typically incorporated into a string of production tubing within a wellbore. The mandrel 26 has a mandrel body 28 which defines a primary flowbore 30 therein. The mandrel body 28 includes threaded upper and lower ends (not shown) which permit the mandrel body 28 to be affixed to neighboring sections of a production tubing string in a manner known in the art. A side pocket 34 is also defined within the mandrel body 28 and is generally parallel to and in fluid communication with the primary flowbore 30. The side pocket 34 preferably includes a pair of cylindrical polished seal bores 38, 40 and an enlarged diameter portion 42 disposed between the seal bores 38, 40. Lateral gas injection passages 44 extend through the mandrel body 28 to interconnect the enlarged diameter portion 42 with the radially surrounding annulus 36.

In operation, the dummy valve 10 is inserted into the side pocket 34 using a running tool in a manner known in the art. The dummy valve 10 is moved generally to the position depicted in FIG. 2 so that the sealing element 22 is located within the seal bore 38 and the sealing element 24 is located within the seal bore 40. Once the dummy valve 10 is in this position, the sealing elements 22 and 24 are swelled to cause them to expand radially outwardly and into sealing contact with the seal bores 38, 40 of the side pocket mandrel 26. In the event that the seal bores 38, 40 have been corroded, eroded or otherwise damaged, the expansion of the sealing members 22, 24 will compensate.

FIGS. 4 and 5 illustrate in further detail the expansion of the sealing members 22, 24 to cause them to seal against the surrounding seal bores 38, 40 by illustrating the upper sealing member 22 in greater detail. The exemplary seal bore 38 in FIGS. 4 and 5 is shown to include a damaged portion 46 which has resulted from erosion or physical impact. FIG. 4 depicts the sealing member 22 in an initial, unexpanded condition, immediately following the dummy insert 10 having been inserted into the side pocket 34. Following insertion, the sealing member 22 is activated to move to its expanded condition depicted in FIG. 5 so that the sealing member 22 expands radially outwardly and against the seal bore 38. Additionally, the expansion of the sealing member 22 will fill in the damaged portion 46, as FIG. 5 illustrates. Typically, an appropriate fluid (water, hydrocarbon, or a mixture thereof) is used in conjunction with the elevated wellbore temperature to expand the sealing members 22, 24. The ambient elevated temperature within the wellbore applies heat to the sealing members 22, 24. In most cases, reservoir fluid containing hydrocarbons and water will be present within the flowbore 30, the annulus 36 and the side pocket 34 when the insert 10 is inserted into the side pocket 34. This fluid will act as the swelling fluid that will saturate and will swell the sealing members 22, 24. Preferably also, a swellable elastomer composition is chosen for the sealing members 22, 24 to be activated by the reservoir fluid (swelling fluid) within the wellbore. In cases where the reservoir pressure within the wellbore cannot support a fluid level to the insertion depth for the insert 10, a plug (not shown) could be placed within the flowbore of the production tubing string below the side pocket mandrel 26. Thereafter, a suitable swelling fluid may be flowed from the surface down through the production tubing string. The swelling fluid will enter the side pocket 34 and saturate the sealing members 22, 24 causing them to swell.

The inventive sealing concept may also be used in conjunction with standard gas lift valves as well as dummy valve inserts. FIG. 6 illustrates an alternative embodiment of the invention wherein the gas lift insert is a gas lift valve 48 which can be removably emplaced within a side pocket mandrel to cause gas from the annulus 36 to be transmitted through the side pocket 34 and into the primary flowbore 30 of the side pocket mandrel 26 and, hence, the production tubing string of which the side pocket mandrel 26 is a part. A suitable gas lift valves for use as the gas lift valve 48 include the Model BCO-1™ (J™, C™, CJ™ injection pressure operated gas lift valve which are available commercially from Baker Oil Tools of Houston, Tex. The gas lift valve 48 carries sealing elements 50, 52, which are fashioned from the same swellable elastomeric material as the sealing elements 22, 24 described previously.

It can be seen that the gas lift inserts 10 and 48 can be used in conjunction with the gas lift mandrel 26 in order to provide a gas lift assembly that can be incorporated into a wellbore production string. The sealing techniques of the present invention may also be used with a number of other inserts that might be used within a side pocket mandrel. For example, swellable sealing elements may be used in conjunction with water flood or chemical injection valves that are emplaced within a side pocket mandrel.

The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention. 

1. An insert for placement within a side pocket mandrel in a wellbore production string, the gas lift insert comprising: an insert body; a sealing element disposed upon the insert body, the sealing element being substantially formed of an elastomeric material that is swellable from a first, reduced-size, condition to a second, enlarged-size condition.
 2. The insert of claim 1 wherein the insert comprises a dummy gas lift valve.
 3. The insert of claim 1 wherein the insert comprises a gas lift valve that is operable to transmit gas.
 4. The insert of claim 1 wherein the sealing element is swellable from the first condition to the second condition in response to fluid saturation by a swelling fluid.
 5. The insert of claim 4 wherein the sealing element is swellable from the first condition to the second condition in response to fluid saturation by water.
 6. The insert of claim 4 wherein the sealing element is swellable from the first condition to the second condition in response to fluid saturation by hydrocarbon fluid.
 7. The insert of claim 1 wherein the sealing element is swellable from the first condition to the second condition in response to heating.
 8. An assembly for incorporation within a production tubing string, the assembly comprising: a side pocket mandrel for incorporation into a wellbore production string, the side pocket mandrel comprising: a mandrel body; a primary flowbore defined within the mandrel body; a side pocket defined within the mandrel body, the side pocket being in fluid communication with the primary flowbore; an insert that is removably disposed within the side pocket, the insert comprising: an insert body that is shaped and sized to reside within the side pocket; and a sealing element disposed upon the insert body, the sealing element being substantially formed of an elastomeric material that is swellable from a first, reduced-size, condition to a second, enlarged-size condition.
 9. The assembly of claim 8 wherein the insert comprises a dummy gas lift valve.
 10. The assembly of claim 8 wherein the sealing element is swellable from the first condition to the second condition in response to fluid saturation.
 11. The assembly of claim 8 wherein the sealing element is swellable from the first condition to the second condition in response to fluid saturation by water.
 12. The assembly of claim 8 wherein the insert comprises a dummy gas lift valve.
 13. A method of sealing an insert within a seal bore of a side pocket mandrel, the method comprising the steps of: disposing the insert within the seal bore; and expanding a swellable elastomeric sealing element to form a seal between the insert and the seal bore.
 14. The method of claim 13 wherein the sealing element is expanded by application of heat and a swelling fluid to the sealing element.
 15. The method of claim 14 wherein the swelling fluid comprises water.
 16. The method of claim 14 wherein the swelling fluid comprises hydrocarbon fluid.
 17. The method of claim 13 wherein the sealing element is expanded by application of heat. 